SMB3: Fix length checking of SMB3.11 negotiate request

The length checking for SMB3.11 negotiate request includes
"negotiate contexts" which caused a buffer validation problem
and a confusing warning message on SMB3.11 mount e.g.:

     SMB2 server sent bad RFC1001 len 236 not 170

Fix the length checking for SMB3.11 negotiate to account for
the new negotiate context so that we don't log a warning on
SMB3.11 mount by default but do log warnings if lengths returned
by the server are incorrect.

CC: Stable <stable@vger.kernel.org>
Signed-off-by: Steve French <smfrench@gmail.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>

diff --git a/fs/cifs/smb2misc.c b/fs/cifs/smb2misc.c
index 5406e95..9df9f0b 100644 (file)
--- a/fs/cifs/smb2misc.c
+++ b/fs/cifs/smb2misc.c
@@ -93,6 +93,41 @@ static const __le16 smb2_rsp_struct_sizes[NUMBER_OF_SMB2_COMMANDS] = {
        /* SMB2_OPLOCK_BREAK */ cpu_to_le16(24)
 };
 
+#ifdef CONFIG_CIFS_SMB311
+static __u32 get_neg_ctxt_len(struct smb2_hdr *hdr, __u32 len, __u32 non_ctxlen)
+{
+       __u16 neg_count;
+       __u32 nc_offset, size_of_pad_before_neg_ctxts;
+       struct smb2_negotiate_rsp *pneg_rsp = (struct smb2_negotiate_rsp *)hdr;
+
+       /* Negotiate contexts are only valid for latest dialect SMB3.11 */
+       neg_count = le16_to_cpu(pneg_rsp->NegotiateContextCount);
+       if ((neg_count == 0) ||
+          (pneg_rsp->DialectRevision != cpu_to_le16(SMB311_PROT_ID)))
+               return 0;
+
+       /* Make sure that negotiate contexts start after gss security blob */
+       nc_offset = le32_to_cpu(pneg_rsp->NegotiateContextOffset);
+       if (nc_offset < non_ctxlen - 4 /* RFC1001 len field */) {
+               printk_once(KERN_WARNING "invalid negotiate context offset\n");
+               return 0;
+       }
+       size_of_pad_before_neg_ctxts = nc_offset - (non_ctxlen - 4);
+
+       /* Verify that at least minimal negotiate contexts fit within frame */
+       if (len < nc_offset + (neg_count * sizeof(struct smb2_neg_context))) {
+               printk_once(KERN_WARNING "negotiate context goes beyond end\n");
+               return 0;
+       }
+
+       cifs_dbg(FYI, "length of negcontexts %d pad %d\n",
+               len - nc_offset, size_of_pad_before_neg_ctxts);
+
+       /* length of negcontexts including pad from end of sec blob to them */
+       return (len - nc_offset) + size_of_pad_before_neg_ctxts;
+}
+#endif /* CIFS_SMB311 */
+
 int
 smb2_check_message(char *buf, unsigned int length, struct TCP_Server_Info *srvr)
 {
@@ -198,6 +233,10 @@ smb2_check_message(char *buf, unsigned int length, struct TCP_Server_Info *srvr)
 
        clc_len = smb2_calc_size(hdr);
 
+#ifdef CONFIG_CIFS_SMB311
+       if (shdr->Command == SMB2_NEGOTIATE)
+               clc_len += get_neg_ctxt_len(hdr, len, clc_len);
+#endif /* SMB311 */
        if (srvr->vals->header_preamble_size + len != clc_len) {
                cifs_dbg(FYI, "Calculated size %u length %zu mismatch mid %llu\n",
                         clc_len, srvr->vals->header_preamble_size + len, mid);

diff --git a/fs/cifs/smb2pdu.h b/fs/cifs/smb2pdu.h
index 253e2c7..0e0a0af 100644 (file)
--- a/fs/cifs/smb2pdu.h
+++ b/fs/cifs/smb2pdu.h
@@ -263,6 +263,13 @@ struct smb2_negotiate_req {
 #define SMB2_NT_FIND                   0x00100000
 #define SMB2_LARGE_FILES               0x00200000
 
+struct smb2_neg_context {
+       __le16  ContextType;
+       __le16  DataLength;
+       __le32  Reserved;
+       /* Followed by array of data */
+} __packed;
+
 #define SMB311_SALT_SIZE                       32
 /* Hash Algorithm Types */
 #define SMB2_PREAUTH_INTEGRITY_SHA512  cpu_to_le16(0x0001)